The present invention relates to a flexible joint for connecting elements for conducting exhaust gases from an automobile engine to the outside such that an angle of connection between the elements is changeable and the exhaust pipes are capable of freely moving relatively toward or away from each other.
As a joint of this type, one disclosed in, for instance, Japanese Utility Model Unexamined Publication No. 86986/1983 is known. The joint disclosed in this publication comprises a bellows tube for preventing the leakage of exhaust gases and connecting together respective exhaust pipes of an engine-side exhaust system and a tail pipe-side exhaust system in such a manner that an angle of connection is changeable and the exhaust pipes are capable of freely moving relatively toward or away from each other, as well as a coil spring for resiliently connecting the exhaust pipes by resiliently restricting the expansion of the bellows tube more than is necessary.
The joint of this type is required to absorb the vibrations of the exhaust pipe of the engine-side exhaust system and prevent transmission of the vibrations to the exhaust pipe of the tail pipe-side exhaust system. With the joint disclosed in the aforementioned publication, however, since the two exhaust pipes are connected resiliently via the coil spring, vibrations based on the phenomenon of mechanical resonance are liable to occur. As a result of this phenomenon of mechanical resonance, there is a possibility that the vibrations are transmitted to the exhaust pipe of the tail pipe-side exhaust system without being dampened, thereby producing unpleasant noise in and outside the automobile and deteriorating the riding comfort of occupants in the automobile.
In addition, with the above-described joint, when the vibration, particularly swinging vibration, of the exhaust pipe of the engine-side exhaust system occurs, the bellows tube is swung with its fixed portion to the exhaust pipe of the tail pipe-side exhaust system as a fulcrum. As a result, large repeated bending occurs to one fixed portion of the bellows tube as compared with the other fixed portion. Mechanical fatigue due to this repeated bending sometimes causes damage to one fixed portion of the bellows tube at an early period.
Meanwhile, although the temperature of the exhaust gases from the engine is about 1100.degree. C., if the exhaust gases of this temperature are brought into direct contact with the bellows tube, the corrosion and deterioration of the bellows tube are promoted. Accordingly, particularly in the case where the joint is formed by using a thin-walled bellows tube as described above, a countermeasure against the exhaust gas temperature is required, but no countermeasure is adopted in the above-described joint.
In addition, since the joint of this type is generally provided on the underside of the chassis in such a manner as to be exposed to and oppose the traveling road surface, there are cases where a thermal shock occurs to the bellows tube as water from the traveling road surface is splashed onto it, and the bellows tube is subjected to the direct impact of stones from the traveling road surface. Hence, there is the possibility that cracks, holes or the like occur in the bellows tube, resulting in the leakage of exhaust gases.